Factors affecting the measurement of thermocouple temperature sensors

Thermocouple temperature sensors have the advantages of wide measurement range, high accuracy, and fast response time, and are widely used in multiple fields. However, in the application process, it is often affected by annoying elements, which can affect the measurement of thermocouple temperature sensors.

How many important factors affect thermocouple measurement are as follows:

1, Pull out depth

The choice of thermocouple temperature measurement point is the most important. The position of temperature measurement points must have representativeness and representativeness for the production process, otherwise the meaning of measurement and control will be lost. When the thermocouple is pulled out of the measured field, heat flow will occur along the length of the sensor. When the temperature is low, there will be heat loss. As a result, temperature deviation occurs between the thermocouple temperature sensor and the measured tool due to temperature deviation. In short, the deviation caused by thermal conduction is related to the depth of extraction.

2, Echoing Time

The fundamental principle of temperature measurement in warfare is that the temperature measuring element must reach thermal equilibrium with the measured tool. Therefore, it is necessary to persist for a certain amount of time when measuring temperature in order to achieve thermal equilibrium between the two. The right and wrong that persist in time are related to the thermal response of temperature measuring elements to time. The thermal response time depends heavily on the structure and measurement conditions of the sensor, with significant differences. For gas media, especially moving gases, it is necessary to maintain equilibrium for at least 30 minutes; For liquids, the fastest time should be at least 5 minutes. For situations where the temperature is constantly changing, especially in the case of sudden changes, if the entire process takes only 1 second, the response time of the sensor request should be in milliseconds.

3, Thermal impedance growth

Thermocouple temperature sensors used at low temperatures, if the measured medium is in a gaseous state, the dust and other particles accumulated in the maintenance tube will melt on the surface, increasing the thermal impedance of the maintenance tube; If the measured medium is a melt, there will be slag accumulation during the application process, which not only increases the response time of the thermocouple, but also causes the temperature to be lower. Therefore, in addition to regular inspections, frequent spot checks are also necessary to increase deviations.

4, Thermal radiation

Pull out the thermocouple temperature sensor used for temperature measurement from the furnace, and heat the heat radiation recovered by the low-temperature object. Assuming that the gas inside the furnace is transparent and the temperature difference between the thermocouple and the furnace wall is large, temperature measurement deviation will occur due to energy exchange. In some cases, in order to increase thermal radiation deviation, it is necessary to increase heat conduction and make the furnace wall temperature as close as possible to the temperature of the thermocouple.